When transporting perishable goods, a conventional air cargo container has inadequate insulation to maintain a controlled temperature environment, such that unacceptably high loss levels of perishable goods are encountered during transport. As such, insulation systems are necessary in order to provide a satisfactory environment for the cargo. However, as discussed in the co-pending application referenced above ("the '684 application"), the specification of which is fully incorporated herein by reference, presently-available refrigerated freight containers which employ a self-contained refrigeration unit are inadequate.
There are advantages of providing an insulation system that can be used to convert a conventional container without the need for more expensive retro-fitting. For many transport businesses, efficient operation depends on the flexibility of handling various types of freight on a daily basis, including both freight that is environmentally sensitive and shipments that are not. Having the capability to convert a conventional container into an insulated container is advantageous to many transport businesses. Presently available means for such conversion are limited in their use as well as being expensive and inconvenient to install. The '684 application discusses the inability of other prior art systems to accomplish ready convertability of a cargo container with a pre-fabricated insulation system that employs a support system that is itself insulative. Such a system is disclosed in U.S. Pat. No. 4,497,859 to Baumann, which discloses an insulating insert consisting of panels of alternating, closely-packed insulating material that are joined along their perimeters to conform to the interior of the transport container. A fluid-tight trough and bottom plate are also provided in the Baumann system, making it cumbersome to install.
The invention described in the '684 application is a freight container insulation system capable of retrofitting a conventional uninsulated freight container, which system includes an adhesive support means for attaching the insulation system to the interior walls of the container, a multi-layer insulated blanket affixed to the adhesive support means, covering the interior container walls to which the adhesive support means is attached, a second multi-layer insulated blanket that is draped across an access opening to the container, and an insulated sheet for placing across the bottom of the container, whereby a controlled environment is created within the confines of the container. The preferred embodiment of that invention includes a plurality of linear insulative strips as the adhesive support means that may be selectively sized and then affixed to the interior walls of the container in a random orthogonal fashion, and wherein the insulated blanket comprises at least one layer of a closed-cell polyethylene and at least one layer of a reflective foil laminate, which may be formed into a roll or be prefabricated and sectioned into discrete individual panels that are sized to cover a corresponding interior container wall, with the insulated sheet for the container bottom constructed of closed-cell polyethylene.
One of the more important features of the invention described in the '684 application is a layer of air provided between the container walls and the installed insulation blanket, thereby incorporating the insulative qualities of air and the reflective qualities of a bright foil laminate as part of the insulation system. Such a system has the advantages of providing a cost-efficient and simplified insulation system that is effective at maintaining a controlled environment.
However, despite the effectiveness of this invention, there remains a need to utilize such a system in the context of cargo which is susceptible to leaks. As may be expected, some perishable goods are liquid based or are made with substances that retain fluid consistencies, which may penetrate the surrounding packing and leak into the interior of the cargo container and ultimately the aircraft. In such events, an insulation system employing individual discretely-constructed panels may not prevent the inadvertent escape of such fluids outside the container.
Depending on the nature of the fluids, a certain amount of damage may result to the interior components of the aircraft. For example, air freight containers are commonly used by the fishing industry for rapid transportation of fish throughout the world. The unfortunate result of shipping large quantities of fish is the undesired accumulation of fish oil in the shipping container. Fish oil is a very corrosive liquid and its inadvertent escape into the cargo area of the aircraft requires the immediate initiation of an expensive cleaning and removal process. Corrosion in the environment of a pressurized airframe can lead to catastrophic structural failure.
In light of the corrosiveness of some liquids, there is a need for a convertible insulation system that is effective at maintaining a controlled environment over relatively long periods and that is leak proof so as to prevent the undesired leaking of liquid cargo into the container and the aircraft.